Convince me to upgrade

I currently have a 2008 E93 335i that I've had for 2 and half years. I love the thing to death but now want more. I've identified a beautiful, low mileage, 2009 E93 M3 (Jerez on Fox red, DCT, Premium/Technology/Cold Weather packages, 19" wheels) which I can get for $20k and my current E93. Test driven it a few times and I can't enough of it. Convince me I should go for this M3 rather than mod my 335i which currently is just stock. I have never actually driven a fully modified 335i to know how it compares.